The local vibrational properties of H2 molecules in crystalline samples were studied by using a first-principles pseudopotential method within the local-density functional approximation and the generalized gradient approximation. The dynamic matrix was calculated by using a super-cell geometry, so that all of the normal vibrational modes were identified for the [100], [110] and [111] orientations of the H2 molecule at, or near to, a tetrahedral site. For the present orientations, a new local mode was found at 650 to 700/cm, which lay above the bulk phonon band, while the vibrational frequencies of the stretching mode ranged from 3556 to 3643/cm. These were close to the experimentally measured value of 3618/cm. Upon allowing for anharmonic effects, the calculated frequencies for the stretching mode were expected to be lowered by about 200/cm.

Local Vibrational Modes of H2 and H2* Complexes in Crystalline Si Y.S.Kim, Y.G.Jin, J.W.Jeong, K.J.Chang: Semiconductor Science and Technology, 1999, 14[12], 1042-7